Ion and electron beam lithographic systems utilize a stencil mask to pattern a resist coated target. These stencil masks typically comprise a substrate and a pattern of openings formed through the substrate. Commonly the substrate will be formed of a semiconductive material, such as silicon. However, other deposited or grown materials, such as SiC, SiN and BN can also be used to form at least some of the substrate.
The formation of a patterned opening extending through substrates comprising silicon, SiC, SiN and/or BN can be quite challenging as such substrates are frequently thin and brittle. Accordingly, it would be desirable to develop alternative methods of forming and patterning openings in such substrates.
Additionally, it can be challenging to maintain the dimension of an opening formed in a thin substrate comprising silicon, SiC, SiN and/or BN, as the material around such openings tends to easily deform (i.e., warp, bow or otherwise alter its shape after formation of the openings). Such deformations can undesirably change the dimensions of the openings and thus alter a pattern of openings formed in a stencil mask substrate. Accordingly, it is desirable to develop methods of maintaining a pattern of openings within a stencil mask substrate.
Stencil masks are typically formed by either a wafer flow method, or a membrane flow method. In a wafer flow method, a full thickness wafer is processed to form a pattern of openings extending into the wafer. The wafer is then reduced in thickness (to a thickness of, for example, from about 2 microns to about 10 microns) to form a membrane. In a membrane flow process, a semiconductive material wafer is first reduced to about a thickness of a silicon membrane. The membrane is then processed to form a pattern of openings through the membrane.